Learning C# 3.0

The Root of All Classes: Object

All C# classes, of any type, ultimately derive from a single class: Object. Object is the base class for all other classes.

A base class is the immediate “parent” of a derived class. A derived class can be the base to further derived classes, creating an inheritance tree or hierarchy. A root class is the topmost class in an inheritance hierarchy. In C#, the root class is Object. The nomenclature is a bit confusing until you imagine an upside-down tree, with the root on top and the derived classes below. Thus, the base class is considered to be “above” the derived class.

Object provides a number of methods that subclasses can override. These include Equals( ), which determines whether two objects are the same, and ToString( ), which returns a string to represent the current object. Specifically, ToString( ) returns a string with the name of the class to which the object belongs. Table 11-1 summarizes the methods of Object.

Table 11-1. The Object class

Method	What it does
Equals( )	Evaluates whether two objects are equivalent
GetHashCode( )	Allows objects to provide their own hash function for use in collections (see Chapter 14)
GetType( )	Provides access to the type of the object
ToString( )	Provides a string representation of the object
Finalize( )	Cleans up nonmemory resources; implemented by a finalizer

In Example 11-4, the Dog class overrides the ToString( ) method inherited from Object, to return the weight of the Dog. You wouldn’t expect to be able to convert ...